Linear lift and counterbalance aircraft passenger door

Abstract

Method and apparatus for vertically lifting a main entry door in an aircraft in order to clear stop fittings and open outward. A hollow shaft having a counterbalance spring and piston therein, which shaft is mounted in a hinge arm and is rotated via a drive chain. The shaft functions to rotate the door by means of splines on the shaft. A door attachment fitting is secured to the top of the piston and slides on the splines during vertical movement of the door.

What is claimed is: 
     
       1. In combination in a vertically lifting aircraft door adapted to clear stop means and open outwardly: a hollow shaft having a counterbalance spring means and piston disposed therein;   a hinge arm;   a drive chain;   said hollow shaft mounted in said hinge arm and rotated by said drive chain;   said shaft having splines for rotating said vertically lifting door;   a door attachment fitting;   said door attachment fitting secured to the top of said piston and capable of sliding on said splines during vertical movement of said door.   
     
     
       2. In a method for vertically lifting an aircraft door, the steps of: rotating a main shaft in a door hinge to position the door;   restricting said main shaft from vertical motion by trapping a upper bearing of a door hinge arm between a main shaft shoulder on top and a retainer sleeve;   transferring a counterbalance spring force to the door from said main shaft through a spring piston threaded into a door attach fitting for spring preload adjustment;   guiding said spring piston in a vertical direction by a linear bearing mounted in the upper end of said main shaft and by a low friction interface between the inner wall of said main shaft and lower end of said spring piston;   providing a slider fitting to match said main shaft for moving vertically on said shaft with said door attach fitting, said slider fitting transferring rotational torque between said door and the door hinge arm.